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Quantitative urine culture methods have become simple, dependable, and inexpensive during the past decade. In research, they have yielded important new knowledge on the biology of urinary infections. Clinically, quantitative urine cultures used in combination with in vitro drug sensitivity tests are the most accurate means available for the diagnosis and treatment of urinary infections.
Bacteriuria exceeding 100,000 organisms per milliliter of urine, which has been properly collected and promptly inoculated, is almost always indicative of infection. In about 80% of such instances, bacteria are also found in the stained urinary sediment. Values of less than 1,000 microorganisms per milliliter of urine are nearly always negative in significance because they usually result from contamination or reflect the normal flora of the urethra. These conclusions have been shown to be equally applicable whether specimens are collected by clean mid-stream voiding, by catheterization, or by suprapubic puncture of the bladder. Results from
BACTERIURIA AND CATHETERIZATION. JAMA. 1960;174(12):1629–1630. doi:10.1001/jama.1960.03030120069015